The is a classic example late ArcheanThe is a classic example late Archean

The Sonakhan greenstone belt of Central Indian Cratonic
(CIC)/Bastar block of central India is a classic example late Archean –
Paleoproterozoic greenstone belt in India. It covers an area of about 1200 sq
km. the sonakhan granite green stone belt trends NNW-SSE direction for about
40km from Sonakhan in the north to Remra (21°17″N: 82°46″E). The Sonakhan group
of Paleoproterozoic divided into lower Baghmara formation, middle formation as
Arjuni and upper Bilari formation. The lower predominantly consists of volcanic
suites, mainly meta-ultramafites, schistose and massive metabasalt,
meta-gabbro, pyroclastics of intermediates to basics composition, ignimbrite,
rhyolites, acidic tuff, pebbly tremolite-actinolite schist, carbonaceous
argillite and ferruginous sulphide-bearing chert.  The upper formation Arjuni unconformably
overlies the Baghmara formation by a thick sedimentary pile and starts with Jonk
river conglomerate. The Jonk river conglomerate mark the unconformity between
the Baghmara formation and Arjuni formation, which is polymictic in nature and
demonstrate bimodality in matrix composition. The matrix is mainly meta –
arkosic and chlorite /biotite rich greywacke but at some place near to Rajadevri
and upto north Arjuni, it is totally replacing by volcanic matrerials. The Jonk
conglomerate is sandwiched between Baghmara and arjuna formation and constricted
to Jonk river only (Das, et.al 1990). The conglomerate horizon is
marked by ill-sorted pebble, cobbles and boulders with preserved striations
marks. The pbbles of granite, gneiss, acidic volcanic rocks, porphyries,
amphibolite, metabasalts, quartzites, quartz veins, BIF, jasper, phyllites and
schists. Since the strain analysis of conglomerates can give the trur results
if the clast matrix ratio is assumed to be low as 90:10. Here the clast versus
matrix ratio varies with average from 90:10 to 10:90. Bilari Group essentially
comprises basic and acid intrusive and extrusive, (Das, et.al.1990). All three-formation
rest on a gneissic basement, the Baya gneissic complex.